Hello guys I have a question I just upgraded from a futaba 7c to the new futaba 8fg man is it a awsome radio so i have a question I never noticed the programming feature Throtle Curve on my 7c but i have it on my 8fg so what exactaly is throtle curve and what does it do</p>

Its used for set-up on HELI's, not planes.

You set the throttle curve to maintain a constant RPM when making pitch changes when flying a heli.

I know........... I have a CP heli, and its Chinese to me to.

Actually, I use the curve on my planes. It give a more linear engine response. 1/8 stick movement on the low end gives alarger change in engine that the same 1/8 movement on the top end. If you program in some expo, curve, you can get the actual engine response to closer match the throttle stick movement. Soften the low end and harden the top.

Writing this, I got to wondering if Expo and Curve are one in the same. Maybe Idon't us the Curve, but I do use expo.

Don

Ya, that's expo, not throttle curve. "Throttle curve" can be set in "steps" and what ever % of throttle you want. On a heli, you move the left stick up and down to change the pitch of the rotor blades. By setting the throttle curve, you can get the RPM to stay somewhat constant while controlling the lift with the pitch. I think...

Well, I've programmed a throttle curve for an airplane not more than a couple of weeks ago. At that time I did notice the similarity. They both show nice graphs on the display. But it's not really expo. Expo is a uniformly changing "curve" (when shown with a graph) whereas the throttle curve changes however it needs to change. The curve can go positive and negative along the graph.

Gasoline engines throttle response is usually anything but linear. A couple of minutes with a tach and the stick movement can give linear response. It's worth it's weight gold.

Not true at all. Throttle curves have a perfectly valid use in airplanes. At the level of the sports flyer, or beginners here, it would be very rare to be used. However, for pattern pilots, 3D pilots, and multi-engine warbird pilots it has uses. Not all carburetors have a perfectly smooth function. It's common for the carb to have "flat spots" and other oddities that make them behave in a way that it not smooth, meaning that the increase in power may not be smooth all the from idle up to full throttle. Using throttle curves can correct that .

But adjusting the way the movement of the servo behaves as you move the throttle stick you can change the way the engine behaves as you advance the throttle. Here is a perfect real world example, multi-engine planes. Because of the geometry of flight when you have more than one engine you want both engines to "pull" the plane the same amount, otherwise you'll start seeing the plane start pull to the side of the engine that is slower. Throttle curves are a way to correct this. On my TFB-25 Ihave the Futaba 9C in it and the throttle curve has 5 points in it. What Ido is Iset all five points and then Iadvance the throttle to each point on that curve, and then check the RPM's of the engines at that throttle setting. If they are the same, or reasonably close, then it's fine and the engines will pull the plane evenly. But if the engines are at different RPM's I can adjust one engine by changing the throttle curve so that at that given throttle setting both engines are spinning at approximately the same RPM's. Ithen do this at each point on the curve. Once I am done Ican advance the throttle from idle all the way to full throttle and both engines will the be exerting the same pull on the plane as they are spinning at the same speeds, which helps keep the plane flying straight.

Throttle curves are a great way to adjust for inconsistencies and oddities in engines, and can be a powerful tool in the hands of an experienced pilot. However, they can also screw them up as well. That's one reason why we rarely talk about them here in the Beginner's Forum, because it's really easy to get into trouble if the pilot doesn't understand what they are doing. This is a point that Imake a lot to beginners as they are learning to fly. Forget about the fancy computer programming in a radio as they learn. It's too easy to simple use the radio to make adjustments on the plane, which can lead to problems. Before any adjustments are made with the radio the plane needs to be be set up mechanically first so that it's as close as it can be to correct. Once that is done then the radio can be used to make any final minor adjustments. But I'll put my soap box away on this, but you get my point.

Ken

You make a good point, and that is a GREAT use of throttle curve. But being in the "RC Airplanes >>> Beginner" thread..........I like my answer better.

Ken, you are right about screwing things up. An example is that I have a Twist 150 that had a Saito 180 engine. It was a second hand plane but never flown. Idid a quick and dirty mechanical adjustment on the throttle and then "fine tuned" it with endpoints, sub trim and expo. Then I had the engine spit off the exhaust pipe. While I'm waiting for Mr Lee to repair it, I put in a Saito 150. Basically the same engine. Iset the mechanical throttle as close as I could eyeball it. Real life running though was now impossible. All of my crutches with the computer radio (10C) while they worked with the mechanical I had on the 180, left the 150 unusable. Back to the basics of setting 100%end points, zero sub trim and no expo and then setting the mechanical put things were the computer could do it's magic again. The basics have to be right or the computer can be a big shovel digging you deeper and deeper into the hole you are in.

For what it's worth, the throttle is the hardest control for me to get right.

Ken, what forum woud be a good one to start a thread expanding on your B-25 throttle setup? I've got a P-61 that has been wating until I got a way to get it to the field and I bought a van this week, so it's time to put it together.

Don

Kind of makes you want to go back to the radios with mechanical servo reversing switches and trim tabs alongside the gimbals. All you had to worry about was flying the airplane, not programming the radio. But just for a moment and then you come to your senses.

Campgems,
 If you are wanting help on the B-25 engines you could ask in either the Warbirds Forum or the Engines forums. However, I dont' hang out in those forums much. You could ask here as well, as long as it's understood that we are offering the advice only for reference.

What does that mean?? Well........ The Beginner's Forum is a strange creature and Minnflyer, CGRetired, myself, and the other moderators that help here have a policy that is unique from most forums on RCU. In other forums on RCU we encourage the talk to stay on topic, and if something doesn't apply to that topic we will either ask the person to start the thread in the correct forum, or we will move it for them. But usually we don't do this here in the Beginner's Forum. Why?? Two reasons. 1) When people are starting out in this hobby they can be "fragile". Think back when you were starting out and you'll understand what I am saying. This hobby can be very intimidating and it can be a bit scary for somebody getting started. They don't want to look "goofy", "like an idiot", or others because they don't know something. And if they come into a forum and are immediately "yelled" at telling them to go somewhere else to get the info it can actually simply chase them away from the hobby, or just RCU (which is just as bad). Think about it. If you are just getting started and you go to a field to find somebody to teach you to fly and they yell at you and tell you to go somewhere else, it's going to affect your interest in the hobby. It's the same thing here. Many may not realize this, but we Moderators  are very VERY protective here in this forum about this very thing, and if we see it happening we will clamp down on it very quickly if it starts happening. We don't want to see anybody lose interest in the hobby because of how they were treated here in the RCU Beginner's Forum. And 2) Almost all information is relative here in the Beginner's forum, even if it doesn't directly involve learning to fly. From the standpoint of a beginner in the hobby they have no clue what is "on topic" and what is "off topic". They are simply hearing different things being talked about and they don't know whether it applies to them or not. And the only way to find out is to ask. Because of this we will allow the discussion of just about anything here in the Beginner's forum so that people just getting started can learn about all the different aspects of the hobby. And when you combine this with #1 we try to do it without yelling at somebody and telling them to go to another forum to look it up. That doesn't mean that we will never redirect discussions to another forum, but for the most part we will try to let most everything be talked about here because it is a learning tool for beginners. If you look back to a lot of posts about things from the more experienced members where they are talking about something above the level of a beginner they will explain it, and then state that it's more advance than the beginner level and should be left alone, or whatever. That's exactly what I did above.

So..... does this help???

Ken